chapter 10 Flashcards
(48 cards)
T cells require _______________as a first signal.
antigen presentation
Once activated, T cells differentiate into their ____________________forms.
effector
Successful T cell–APC interactions organize signaling molecules into an ____________________, which consists of TCR/MHC-peptide complexes and adhesion molecules/bound ligands.
immunological synapse
additional signal that is required to induce proliferation of antigen-primed T cells and is generated by interaction of CD28 on T cells with CD80/86 on antigen-presenting cells
costimulatory signal
What is required for optimal T-cell activation and proliferation?
costimulatory signals
costimulatory signal 1:
antigen-specific TCR engagement
costimulatory signal 2:
contact with costimulatory ligands
costimulatory signal 3:
cytokines directing T-cell differentiation into distinct effector cell types
function of positive costimulatory receptors?
facilitate activation
-examples are CD28 ICOS
function of negative costimulatory receptors?
help turn activation off
-examples are CTLA-4, PD-1, and BTLA
describe CD28 and its functions:
-Generally involved in initial activation events in T cells
* 44 kDa glycoprotein homodimer expressed on majority of T cells
* Markedly enhances TCR-induced proliferation and survival
* Binds to B7-1 and B7-2 expressed by APCs
describe ICOS and its functions:
-expressed on memory and effector T cells
-inducible costimulator, binds ICOS-ligand on activated APCs
-may help to maintain activity of already differentiated cells
describe CTLA-4 and its functions:
-Induced within 24 hours after activation, peaks 2–3 days post-stimulation
- Binds to B7-1/B7-2 with higher affinity than CD28 but shuts down signaling pathways (“putting the brakes on”)
What does PD-1 stand for?
program death 1
what does BTLA stand for?
B- and T-lymphocyte attenuator
may help to mediate T-cell tolerance in nonlymphoid tissues
PD-1
may downregulate inflammatory and autoimmune responses
BTLA
-a physiological state in which cells are unable to be activated by antigen
-results if a costimulatory signal is absent
-helps provide tolerance
-if only signal 1 is received, the cell is rendered nonresponsive
clonal anergy
Which signal do cytokines provide?
signal 3
describe how IL-2 is an example of an autocrine type of cytokine response system:
-T cells produce the cytokine and receptor for it
-binding of this ligand induces a very strong proliferation signal during activation stages
what type of characteristic costimulatory properties do APC cells have?
they provide the right signals to activate T cells
Viral/bacterial proteins that bind to specific Vβ regions of TCRs and α chain of class II MHC molecules
superantigen
superantigens non-specifically, effectively “short-circuits” TCR and MHC-peptide, which produces what?
dramatic cytokine secretion by large proportion
of inappropriately activated T cells
Initial activation signals 1 and 2 induce:
-upregulation of prosurvival genes
-transcription of IL-2 and IL-2R genes
-outcome is activation and proliferation
